In Belgium and in other countries, the Cancer Registry data show an increased incidence of cancers related to age, the majority of tumors being diagnosed beyond 60 years. However, the mechanisms responsible for this increase are not clear. Cancer could be chronologically associated with aging because of the long latency period between the exposition to carcinogenic agents and the appearance of clinical signs. Aging could also predispose directly to cancer by different mechanisms (impaired immune response, increased oxidative stress, shortening of telomeres, accumulation of senescent cells). In this review, we propose to describe different hypotheses which could explain the increased incidence of cancers in the elderly.